(a) Technical Field
The present disclosure of invention relates to a display device and a driving method thereof, and more particularly, to a display device and a driving method thereof that may increase a charging rate.
(b) Description of the Related Technology
A display device, such as a liquid crystal display (LCD) and an organic light emitting diode (OLED) device, generally includes a display panel including a plurality of pixels and a plurality of signal lines and one or more drivers configured to electrically drive the display panel.
Each pixel includes a switching element connected to a signal providing line, a pixel electrode connected to the switching element, and a counter electrode or counter electrode portion opposing the pixel electrode. The switching element may be one such as a thin film transistor (TFT) which receives a data voltage by way of the signal providing line. The counter electrode may be formed over a whole surface of the display panel and may be applied with a common voltage Vcom. The pixel electrode and the counter electrode may be positioned on a same substrate and/or they may be positioned on different substrates.
The display device receives an input image signal from an external graphic controller. The input image signal contains luminance information for controlling each pixel and the desired luminance for each pixel has a respective and predetermined grayscale value. Each pixel is then driven with a data voltage corresponding to the desired luminance. A data voltage applied to a pixel appears as a driving electric field or current based on a difference with a common voltage applied to a common electrode. Each pixel displays a luminance at which a gray of an image signal appears, based on the pixel voltage. Here, to prevent a degradation phenomenon from occurring when an electric field of a single direction or a current having an identical polarity is applied for too long a time, it is possible to reverse a polarity of a data voltage with respect to a reference voltage for each frame, for each row, for each column, or for each pixel. The corresponding techniques are sometimes referred to as row inversion, column inversion, and dot inversion.
One of the drivers of the display device is a gate lines driver configured to supply gate signals to gate lines of the display panel. Another of the drivers is a data lines driver configured to supply data signals to corresponding data lines of the display panel. The display device typically also has a signal controller configured to control the data lines driver and the gate lines driver, and optionally other modules (e.g., backlighting unit) of the display device.
The gate lines driver may include a shift register including a plurality of stages subordinately connected to each other, or at least one gate line driving circuit. The gate lines driver receives a plurality of driving voltages and a plurality of gate control signals to generate its corresponding gate signals. The plurality of driving voltages may include a gate-on voltage (Von) capable of turning on a switching element and a gate-off voltage (Voff) capable of turning off the switching element. The plurality of gate control signals may include a scanning start signal STV for instructing a start of scanning, a gate clock signal CPV for controlling a timing for outputting each gate-on pulse, and the like. The gate lines driver sequentially outputs gate-on pulses of respective gate signals sequentially to corresponding ones of the gate lines.
Every time a gate-on pulse is supplied to a corresponding gate line, the data lines driver supplies a corresponding set of data voltages to respective ones of the data lines such that the supplied data voltages may be applied to respective ones of the activated pixels through their respective switching elements.
Currently, a high quality image may be provided according to an increase in a resolution of a display device and thus, there is a trend that the resolution of the display device is increasing. Accordingly, an amount of time for supplying (e.g., charging) each pixel with a corresponding input data voltage may be decreased according to the increase in resolution because there are more rows of pixels to be driven per frame period when the vertical resolution of the display is increased. In particular, when reversing of polarity of the supplied data voltages is involved, an amount of time for charging a respective data voltage into a corresponding pixel so as to reach the desired positive or negative target data voltage may be insufficient.
A pre-charging driving method has been generally used to improve charging time. The pre-charging driving method may transfer a pre-charging voltage by way of a corresponding data line and in advance before applying the desired target data voltage to the corresponding pixel to thereby more quickly reach the positive or negative target pixel voltage for thereby producing a target luminance when performing a main charging of the corresponding pixel. However, transmitting pre-charge levels along the data lines can consume part of the signal bandwidth capability of the data lines, switching between the pre-charge levels and the target levels of the image can consume part of the signal bandwidth capability, and the data lines are at the same time loaded by parasitic capacitances of the pixels operatively coupled thereto.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the here disclosed technology and as such, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to corresponding invention dates of subject matter disclosed herein.